Microstructure and piezoelectric properties of 0.95(Na0.5K0.5)NbO3–0.05BaTiO3 ceramics

Abstract

For 0.95(Na0.5K0.5)NbO3–0.05BaTiO3 (0.95NKN-0.05BT) ceramics sintered at 1040–1075°C, abnormal grain growth occurred but the grain size decreased when the sintering temperature exceeded 1075°C. The dielectric constant (ϵ3T∕ϵ3), electromechanical coupling factor (kp), and piezoelectric constant (d33) were considerably increased with increasing relative density and grain size. Evaporation of Na2O deteriorated the piezoelectric properties by decreasing the resistivity. To minimize Na2O evaporation, specimens were muffled with 0.95NKN-0.05BT powders during the sintering. Improved piezoelectric properties of d33=225pC∕N, kp=36%, and ϵ3T∕ϵ3=1058 were obtained for specimen sintered at 1060°C for 2h with muffling.

A generalized rule for large piezoelectric response in perovskite oxide ceramics and its application for design of lead-free compositions

“…Modified compositions and solid solutions in the systems ͑Bi, Na͒TiO 3 ͑BNT͒, ͑Bi, K͒TiO 3 ͑BKT͒, BaTiO 3 ͑BT͒, and ͑K,Na͒NbO 3 ͑KNN͒ have received considerable attention as the potential lead-free candidates but reported results are still inferior to that of PZT. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Design of new lead-free composition is challenging as formulations derived using structure maps, tolerance factor approach, electronegativity factor, and ab initio calculations have not resulted in any promising material. Naturally, the question that comes to mind is "how to design a lead-free composition and predict its approximate piezoelectric response?."…”

Polymorphic Phase Transition and Temperature Coefficient of Capacitance of Alkaline Niobate Based Ceramics

“…It might be contributed by the formation of the liquid phase due to sintering temperatures over 1,150℃. On the other hand, it became more dense and small, because the liquid phase played key roles of inhibitor for grain growth as increasing sintering temperatures in Excess NKN [9]. Figure 5 shows the relative density of No excess NKN and Excess NKN with increasing sintering temperatures.…”

Alkali Niobate Piezoelectric Ceramics

“…There have not been significant problems of degradations of the ceramics originating from the relatively low phase transition temperature around 200 C at which the ferroelectric phase changes to the antiferroelectric phase, and their piezoelectricity disappears. Alkaline niobate perovskite ceramic materials have been studied by a number of researchers [146][147][148][149][150], because of their attractive properties such as high acoustic vibration velocities, high Curie temperatures, and relatively high electromechanical coupling properties. One of the earliest studies on the alkali niobate ceramics was done by Shirane, Newnham, and Pepinsky on ferroelectric properties of KNbO 3 -NaNbO 3 (KNN) binary system [58].…”